Wired radio change-over system



H. R. 'BUTLER `WIRED RADIO CHANGE-OVER SYSTEM Dec. 19, 1939.

Filed March 3, 1958 munom 22.51522 zmwmmm mii INVENTOR Patented Dec. 19,1939 UNITED STATES i 'amasar WIBED RADIO CHANGE-OVER` SYSTEM,

Henry R.. Butler, Verona, N. J., assigner to Wired Radio, Inc., NewTurk, N. Y., a corporation o! Delaware Application March 3,1938, serialNo. 193,646

-s claims. (ci. 11s- 15) This invention relates in general to asignalling system and especially relates to an arrangement forinterposing special signals on a multi-program transmission system. Theprincipal object of the invention consists in `providing a system fornormally transmitting programs with' means for interposing on saidsystem a special signal, such as an alarm, instructions, or the like, incases of emergency or necessity,

A further object of the invention comprises providing a multi-channelprogram system for tra'ns- :mitting programs at a vplurality ofdiiferent frequencies to selective receivers with'means for.

interposing a special signal on all of said program channels so that areceiver tuned to any one of the program channels will receive a specialsignal. These and other objects will be apparent from the following,reference being had to theaccompanying drawing which represents oneembodiment of the system of the invention.

' The invention will be described in connection with a wired radiosystem, although it will be apparent that other forms of signallingsystems can equally well adopt the concept of the invention.

According to the invention, a base frequency source i, such as anelectron tube oscillator, supplies a sustained high frequency wave of abase frequency such as, for` example, 13 kiloc'ycles.

This wave is fed to a harmonic generator 2 which develops a plurality ofharmonic waves of different frequencies from the base frequency wave.These frequencies, such as 26, 39, 52, and 65 kilocycles, arerespectively supplied to modulators s` 3 6. The modulators 3-6 compriseelectron circuit means known-in the art for modulating high frequencywaves with signals. The modulators 3-'6 have their input circuitsconnected to double pole switch arms 1-l0. These switch arms are 40shown contacting terminals connected with modulation sources i-I-I 4respectively. The switches may be moved commonly to engage otherVterminals connected in parallel with an emergency modulation source I5.Accordingly, it will be 45 seen that the modulators 3-6 may be connectedeither with the modulation sources I I-ll respectively, or in commonwith the emergency modulation source I5.

The output circuits of modulators vIi6 are 50 directed through poweramplifiers IG--liiand thence through lters 2li-23. The lters 20-23restrict the respective outputs to discrete fre- -quency bandsimpressed' through capacitive couplings upon the transmission medium 25.The

transmission medium 25 here shown is a commercial power distributionnetwork connected with receivers having selective filter circuits andreceiv'ing any one of the program channels trans- Y mitted through thevarious lters. The modula' tion sources iI-M comprise different program5 `sources for supplying various program signals to the differentmodulators. The emergency modulation source l5 supplies emergency orpredetermined signals. Itmay be provided with a phonograph for supplyingprel0 determined Isignals at predetermined times, as controlled by aclock driven switch, or may be provided with a microphone such asmicrophone 26, under control of an emergency operator. The emergencyoperator might be the captain of a l5 ship, the superintendent of abuilding, or the chief of police or re chief of a township, who makes anannouncement of vital importance to the receivers connected with thetransmission medium 25.

As shown in the drawing, the microphone cir- 20 cuit includes atransformer connection 2 to a rectier-relay'28 which, upon beingenergized by signals in the transformer ZTI, operates a power relay tooperate a slow-'to-release electromagnet 29' controlling an armature Si)mechanically con- 25 .nectd with `switch arms i-m When the electromagnet29 is energized, the switches ie-l@ are pulled against tensioning spring3i so asto engage contactsv connected with emergency modulation source.i5 and thereby connect all of'modu'lators 30 3 6 in common with theemergency modulation source so that the emergency signals aretransmitted over the transmission medium. Thus, no matter to whatprogram signal the receivers are tuned, they will receive the emergencysignals. The electromagnet 29 will not release the switch arms 1-I0until a predetermined time has lapsed after energization of transformer21 by the emergency signals.

Although a preferred form of system has been 40 disclosed, it will berecognized that various changes and modifications can be made by thoseskilled in the art without departing from the intended scope of theinvention. Therefore, no limitation is intended except as pointed out inthe appended claims.

What is claimed as new and original to be secured by Letters Patent ofthe United States is: l

1. A signalling system comprising, a common transmission medium,transmissionmeans for transmitting a plurality of different programs'atdiscrete frequencies over said transmission medum, an emergencymodulation source, and control means for interrupting said programtransmission and` connecting said emergency modulation sourcewwith saidtransmission means to simultaneously transmit the single emergencysignal modulation at all of said frequencies, said emergenoymodulationsource comprising means responsive to the emergency modulations for ac--tuating said control means.

2. A signalling system in accordance with claim 1 in which saidtransmission means includes a plurality of modulators and a plurality ofmodulation sources respectively connected to said modulators in normaloperation, and in which said control means is adapted to disconnect allsaid modulation sources from said modulators and connect said emergencymodulation source in common with all of said modulators.

3. A signalling system in accordance with claim 1 in which saidtransmission means inciudes means -for generating a plurality ofharmonically related discrete carrier frequencies, a plurality ofdiierent modulation sources, a plurality of mod- -ulators forrespectively modulating said diierent carrier frequencies with themodulation signals i from said diierent sources, and in which said cuitsof, said modulators, connections .to said switches for connectingl saidprogram modulation sources respectively with said modulators or forconnecting said emergency modulation source in common with all of saidmodulators for transmitting an emergency modulation signal at all ofsaid discrete carrier frequencies, and means responsive to the emergencymodulations for operating said switches to effect immediately saidcommon connection and return to said respective connections apredetermined period after cessation of the emergency modulations.

5. A signalling system in accordance with claim 4 includingelectromagnetic means for controlling said switches, and circuitsextending from said emergency modulation source to said electromagneticmeans for `controlling the same to tiein said emergency modulationsource with all of said modulators.

6. In a system for transmitting a plurality of carriers over a wirenetwork to a multiplicity of receivers, each carrier being modulated bya separate program source in normal operation, a cutin devicecomprising, a source of special modulations, a relay actuated by saidmodulations, and a switch operative in response to said relay fordisconnecting all said program modulation sources and connectingsaidspecial modulation source to all said carriers immediately upon theoccurrence oi special modulation, said switch being adapted to hold thelatter connection for a predetermined time after cessation of said relayactuation.

Y HENRY R. BUTLER.

